Design improvement of the bottom guide of a material irradiation capsule : dowel pin type

A material capsule system was developed for an irradiation test of non fissile materials in HANARO. The capsule system has been actively utilized for the various material irradiation tests requested by users from research institutes, universities, and the industries. 12 instrumented and 2 non-instrumented capsules have been designed, fabricated and successfully irradiated in HANARO CT and IR test holes since 1995. Because of the up-stream of the coolant in HANARO, the instrumented capsule is supported or fixed at 4 points of the capsule main body and protection tube to satisfy the seismic requirements of the reactor. The instrumented capsule is fixed to the reactor flow tube by a bottom guide assembly of the main body. First bottom guide assembly of an instrumented capsule that was used in a high pressure and velocity of the coolant was designed and fabricated on the basis of the design of the HANARO drive fuel and has been partially modified due to various undesirable matters which occurred during the irradiation tests of the capsules. From the 03M-06U capsule, a new type of bottom guide assembly (B(bolt) type) was designed and applied to solve these problems and it's integrity was proven through in- and out-pile tests. However, several undesirable technical points about the bolt type bottom guide were discussed at a specialist committee. Therefore, another type of bottom guide assembly (C(dowel pin) type) was designed and fabricated according to the committee's suggestion to solve the technical points. The new design will be applied to all of the material and creep capsules in HANARO